1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for determining integrity of cement sections in wellbores.
2. Background of the Art
Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Modern wells can are drilled to great well depths, often more than 15,000 ft. Hydrocarbons are trapped in various traps or zones in the subsurface formations at different wellbore depths. Such zones are referred to as reservoirs or hydrocarbon-bearing formations or production zones. A casing is generally placed inside the wellbore and the space between the casing and the wellbore (annulus) is filled with cement. A production string or assembly containing a number of devices is placed inside the casing to perform a variety of operations downhole, including, but not limited to, fracturing, treatment and production of fluids from the formation to the surface. Once the well is no longer productive, a section of the well is filled or plugged with cement and abandoned. In some other cases, plugs made of other materials may be placed in the well prior to abandoning the well. It is important to determine that integrity of the cement plug or other plugs or prior to abandoning the well. Pressure tests are commonly performed to determine the integrity of the cement and other plugs. Such methods, however, do not provide long term information about the ongoing integrity of the cement plugs.
The disclosure herein provides apparatus and method for detecting leaks, such as of hydrocarbons, through the cement and other plugs to provide ongoing information about the integrity of the cement and other plugs.